A human heart includes four heart valves that determine the pathway of blood flow through the heart: the mitral valve, the tricuspid valve, the aortic valve, and the pulmonary valve. The mitral and tricuspid valves are atrioventricular valves situated between a respective atria and ventricle, while the aortic and pulmonary valves are semilunar valves situated between a respective ventricle and the aorta or pulmonary artery, respectively. Ideally, native leaflets of a heart valve move apart from each other when the valve is in an open position, and meet or “coapt” when the valve is in a closed position. Problems that may develop with valves include stenosis, in which a valve does not open properly, and/or insufficiency or regurgitation, in which a valve does not close properly. Stenosis and insufficiency may occur concomitantly in the same valve. The effects of valvular dysfunction vary, with regurgitation or backflow typically having relatively severe physiological consequences to the patient.
Recently minimally invasive approaches have been developed to facilitate catheter-based implantation of a valve prosthesis on a beating heart that are intended to obviate the need for the use of classical sternotomy and cardiopulmonary bypass. More particularly, flexible prosthetic valves supported by stent structures that can be delivered percutaneously using a catheter-based delivery system have been developed for heart and venous valve replacement. These prosthetic valves may include either self-expanding or balloon-expandable stent structures with valve leaflets attached to the interior of the stent structure. The prosthetic valve can be reduced in diameter, by crimping onto a balloon catheter or by being contained within a sheath component of a delivery catheter, and thereafter advanced through the venous or arterial vasculature. Once the prosthetic valve is positioned at the treatment site, for instance within an incompetent native valve, the stent structure may be expanded to hold the prosthetic valve firmly in place.
A heart valve prosthesis employed with catheter-based, or transcatheter, procedures generally includes an expandable frame or stent that supports a valve body having a plurality of leaflets. The frame can be contracted during percutaneous transluminal delivery, and expanded upon deployment at or within the native valve or within a previously implanted prosthetic heart valve. Certain heart valve prostheses are configured to be initially provided in an expanded or uncrimped condition, then crimped or compressed about a balloon portion of a catheter. The balloon is subsequently inflated to expand and deploy the prosthetic heart valve. In other heart valve prostheses designs, the frame is formed to be self-expanding. With these systems, the heart valve prosthesis is reduced to a desired delivery diameter and held in that compressed state within a sheath for transluminal delivery. Retracting the sheath from covering the heart valve prosthesis allows the frame to self-expand toward its original, larger diameter and into apposition with the native valve site.
The actual shape or configuration of any particular prosthetic heart valve to be delivered in a transcatheter implantation procedure is dependent, at least to some extent, upon the native heart valve being replaced or repaired, i.e., mitral valve, tricuspid valve, aortic valve, or pulmonary valve. The frame must oftentimes provide and maintain a relatively complex shape in order to achieve desired fixation with the native anatomy and with self-expanding frame designs, the frame can experience significant, rapid radial expansion upon deployment from the sheath. Taken in combination, these design features can give rise to delivery concerns. A rapidly expanding frame having one section expanding to a substantially larger diameter than an adjacent section, for instance, can cause the prosthetic heart valve to spring off of the delivery device in a relatively uncontrolled fashion. This rapid deployment can, in turn, result in the valve body being improperly positioned. For example, exemplary prosthetic mitral valve designs can have an inflow diameter on the order of 60 mm, with an inflow section of the frame extending perpendicular, or nearly perpendicular, to an outflow section of the frame having an outflow diameter on the order of 30 mm. During transluminal delivery to the native mitral valve, the frame may be held in a compressed, nearly cylindrical shape with a diameter on the order of 12 mm. The inflow section is intended to self-expand into apposition with the atrium with the outflow section of the prosthetic mitral valve self-expanding into engagement with the native annulus. If a delivery system does not have a mechanism to control expansion of such a self-expanding frame, the inflow section of the frame can experience rapid, uncontrolled expansion upon deployment, such that the outflow section may seat improperly within the native mitral valve annulus, and such that the inflow section may fail to anchor sufficiently within the corresponding anatomy of the atrium.
Delivery systems that provide controlled deployment of a prosthetic heart valve having a self-expanding frame are shown and described in U.S. application Ser. No. 14/519,242 filed Oct. 21, 2014, which is incorporated by reference herein in its entirety. Such delivery systems may alleviate issues that can arise due to rapid, uncontrolled expansion of an inflow section of a self-expanding prosthetic heart valve, and also provide for recapture of the self-expanding prosthesis prior to full deployment. Although the delivery systems and techniques disclosed in the '242 application provide improvement over prior prosthetic heart valve delivery systems, there remains a need for continued improvement of such systems. For instance even after a self-expanding valve prosthesis is properly positioned, paravalvular leakage is still a concern as leakage may occur at the time of implantation or may occur after implantation due to changes in the native anatomy, such as elongation of the chordae tendinae, stretching of the native leaflets over time due to the stresses placed thereon by the functioning of a prosthetic mitral valve, and/or the migration of the papillary muscles over time due to the remodeling of the heart that over time. In order to address concerns regarding paravalvular leakage, embodiments hereof relate to a delivery system having the additional functionality of guiding a stapling or anchoring tool to an area of the heart valve prosthesis that may be in need of or may benefit from additional anchoring to tissue of the heart, such that the additional anchoring may further minimize relative movement between the prosthesis and the heart to prevent paravalvular leakage.